1. Field of the Invention
The present invention relates to a position deviation order detection method, an image position deviation correction method, a streak unevenness correction table creation method, and a streak unevenness correction method, and more particularly, relates to a position deviation order detection method for detecting a position deviation of an image generated when the image is printed out by an inkjet printer in which plural inkjet heads are arranged in a sub scanning direction and is read using a scanner, an image position deviation correction method for correcting a position deviation of an image using a streak unevenness correction chart having a density image pattern corresponding to a size (order) of the position deviation of the detected image, a streak unevenness correction table creation method for creating a streak unevenness correction table for correcting streak unevenness generated in an image printed by an inkjet printer, and a streak unevenness correction method for correcting streak unevenness generated in an image using the created streak unevenness correction table.
2. Description of the Related Art
In recent years, a technique of printing a desired image on a recording medium such as soft packaging members made of PET or the like which are successively transported, by an inkjet printer using an elongated inkjet-type head, has been used. In the inkjet printer, density unevenness (density non-uniformity) occurs in a printed image due to variation of ejection characteristics of multiple ink ejection nozzles (printing elements) provided in inkjet heads, which causes problems in image quality.
In order to correct density unevenness, JP2012-066516A discloses a technique of outputting and measuring a density measurement test pattern using an inkjet printer to obtain a density unevenness correction value for each printing element, performing density unevenness correction using the density unevenness correction value for each printing element, and obtaining an image without density unevenness.
JP2012-066516A relating to a patent application of the applicant discloses a technique of printing out a density measurement test pattern including plural gradation values that vary in a sub scanning direction using an inkjet recording device, measuring the output density measurement test pattern, calculating a characteristic function for each recording element from measurement values and input gradation values used in printing, calculating a reference characteristic function from input measurement values obtained using an inverse function of the characteristic function and an average output gradation value, acquiring output measurement values as the input gradation values from an inverse function of the reference characteristic function, acquiring output gradation values from the inverse function of the characteristic function using the output measurement values as inputs, calculating the acquired output gradation values as unevenness correction values in the input gradation values, and performing unevenness correction so that differences between the input gradation values and the output gradation values are not generated.
On the other hand, JP2004-330497A discloses a technique relating to an inkjet printer having a characteristic print method based on an inkjet head and provided with an ejection head mounted on a carriage that reciprocates in a main scanning direction, in which when recording an image or the like by bidirectional printing (shuttle printing) in which an ink is ejected while the ejection head is reciprocating on a printing sheet transported in a sub scanning direction, a correction pattern having a density difference in the main scanning direction is formed in order to correct unevenness generated between a dot formation position on a forward path in the main scanning direction and a dot formation position on a return path in the main scanning direction, the density of the formed correction pattern is read, and the unevenness is corrected using the read density information. The disclosed correction pattern is a lattice pattern having a density difference in the main scanning direction.